That's good news because blue means customers in those areas can start flushing their homes' and businesses' pipes — and after that, start using their water again for cooking, cleaning and drinking.

West Virginia Gov. Earl Tomblin said that by Tuesday night, "more than one-third of the affected customers have had safe water restored," NPR's Hansi Lo Wang reports. Some 300,000 people had been without water since last Thursday.

The latest word from West Virginia American Water is that "Current test results show zero detection of MCHM at the Kanawha Valley Water Treatment Plant intake" near the Elk River, the body of water that was contaminated by a chemical leak (of MCHM, or methylcyclohexene methanol) last Thursday.

We've updated this post with information as its come out. See more updates below.

Update at 9:20 p.m. ET: Safe Water Restored To 'More Than A Third'

Gov. Earl Tomblin's statement read in part:

"More West Virginians have seen the DO NOT USE order lifted for their area and have been asked to begin the flushing process. More than one-third of the affected customers have had safe water restored. West Virginia American Water Company reports that samples taken at its treatment plant intake now show no presence of the chemical.

"The DO NOT USE order remains in place for other areas. I ask residents in these areas to be patient and refrain from beginning the flushing process. "

Update at 6:35 p.m. ET: Water-Use Bans Lifted In Some Areas

Water customers near Alum Creek and Upper Falls can now use their water, officials say.

Update at 4:45 p.m. ET: More Customers Get All-Clear

The "do not use" order has now been lifted for some 38,000 water customers, state officials announced this afternoon. And in addition to Kanawha County, school has been cancelled for tomorrow in Lincoln, Boone, and Putnam Counties, Hansi tells us. We've updated our map to reflect the changes.

Update at 2:15 p.m. ET: Map Was Incorrect; Schools Closed Weds.

After we noticed a discrepancy in this morning's water-safety map and the one being displayed today — in which the South Hills area went from blue to red — Hansi passed along word that a correction was made.

"It was an error. South Hills back to red on the map," says Lawrence Messina, communications director for West Virginia's Department of Military Affairs and Public Safety, via Twitter.

And according to a Twitter feed that relays weather-related school closings in the state, "All schools in #Kanawha Co closed Wed 1/15/14 due to water crisis code A employees report at regular time."

It was last Thursday when a chemical used in coal processing leaked into the Elk River near Charleston and then into the region's water supply system. Residents and businesses across nine counties were warned not to use the water coming from their taps because the chemical — methylcyclohexene methanol — can cause severe burning in the throat, vomiting and skin blistering.

On Morning Edition today, NPR's Daniel Zwerdling reported that a team of federal investigators from the Chemical Safety Board is going to look into the leak.